Medically reviewed by Susan Kerrigan, MD and Marianne Madsen
Gene therapy is the practice of treating or preventing disease by inserting new genetic material into a patient’s cells to change the way their body acts and reacts. It is most commonly mentioned as a means to replace a malfunctioning or mutated piece of DNA; the new gene is transmitted by benign viruses known as adenoviruses, which replicate and disseminate it throughout the body. The therapeutic gene enters a lysogenic state and integrates into the hosts genes; when a cell attempts to read or replicate the genetic codes of the faulty gene, it will instead read the therapeutic gene, causing the body to execute its processes normally.
One major application for this is in treating hemophilia A, a disease caused by a mutated protein known as Factor VIII that prevents the blood from clotting properly. This condition is far more common than hemophilia B, occurring both through hereditary transmission and spontaneous mutation; it afflicts all racial or ethnic groups equally and degenerates into severe hemophilia in more than fifty percent of the cases.
Gene Therapy for Hemophilia A
Because the condition involves a protein being continually replenished in the body, gene therapy shows particular promise for treating it; the new genes will be read relatively quickly, and the corrected protein is introduced into the bloodstream in short order. As the adenovirus vector will make the gene a permanent part of the patient’s genetic code, there will be no need for a second dose; with the current conventional therapy including daily injections of Factor VIII, that alone represents an enormous leap forward. Another significant benefit is found to be in the relative safety of gene therapy; once a gene is introduced, there can be no bad doses, supply shortages, or problems during injection.
A recent breakthrough has indicated that gene therapy for hemophilia A, and with it many other gene associated diseases, is on the verge of becoming publicly available from a company called BioMarin. After a three-year study into its effectiveness, the drug has shown proven results among over one hundred fifty patients and is in the final stages of FDA approval in the United States. Officials have already labeled this treatment a ‘breakthrough drug’ and approved it for larger scale uses, putting it the farthest along any gene therapy treatment for hemophilia has ever gotten in the approval process.
Legislative Delays
A recent revision of a previously promising ruling by the FDA has thrown much of the progress into doubt; shortly before gaining approval, the Administration changed the criteria needed to sanction Roctavin, one of the leading prototypal gene therapy drugs. The decision comes along with the request for extended testing periods and added documentation, with the net effect that Roctavin will be approved in the last quarter of 2021 at the earliest.
The FDA’s decision was based on differences between studies conducted in the first two phases of testing and the third, making the original test unreliable as the basis for further study and eventual marketing. Other countries have noted the FDA’s concerns and begun to subject Roctavin to additional phases of testing as well.
Roctavin had previously been granted two special statuses: breakthrough therapy, which immediately confers all FDA fast-track benefits, and orphan drug, which waives fees and offers tax credits for the drug in the trial stages. While neither has been revoked, the FDA’s decision shows that a more thoroughly established record of clinical success will be needed to make gene therapy available to the wider hemophilia A market.
The Costs
Prohibitively expensive treatments are nothing new to the chronic disease community, but gene therapy drugs have set a new bar; the price of a single patient’s treatment is expected to reach or exceed three million dollars. Insurers are quick to balk at such prices, but even the ‘subscription’ plan of roughly half a million a year for five years has made many agencies back off.
Many patient advocacy groups have expressed displeasure over these prices, decrying them for taking advantage of the patient community. Manufacturers have pointed out that this is the cost instead of buying Factor VIII injections or pills; as a once in a lifetime expense they argue, it should be well worth it to be rid of the disease for good.
Conclusion
Hemophilia A is on the verge of a proven and permanent solution by way of gene therapy, with only a few more steps before being fully approved by the FDA. It is likely to lead the way for many other gene therapies, but to be truly accessible to the public, it must undergo a price correction to put it in reach of the common patient.
References
- How does gene therapy work?
- Hemophilia A
- Gene Therapy for Hemophilia A
- Multiyear Follow-up of AAV5-hFVIII-SQ Gene Therapy for Hemophilia A | NEJM
- Frequently Asked Questions: Breakthrough Therapies | FDA
- Designating an Orphan Product: Drugs and Biological Products | FDA
- Gene Therapy Shows Promise For Hemophilia, But Could Be Most Expensive U.S. Drug Ever
